The present invention relates to a method of forming a mask with an opening pattern used for a charged particle beam exposure; which comprises the steps of: outlining a pattern figure represented by prescribed pattern data; descerning whether every polygonal pattern represented by pattern data being obtained through said contouring is a convex polygon or not; splitting every polygonal pattern which is not identified as a convex polygon into a plurality of pattern sections; and distributing a plurality of said pattern sections onto masks which constitute a set of complementary masks. In the present invention, any of singular patterns which may cause a problem in stencil mask formation is, through systematical identification, extracted and then, this singular pattern is split and distributed onto different masks constituting a set of complementary masks so that, while maintaining sufficient mechanical strength, the number of openings can be reduced to a minimum by avoiding superfluous pattern splitting. As a result, a stencil mask capable to improve the reliability of the pattern projection can be provided efficiently.
A pattern of a transfer mask to transfer, by the use of energy beams, a transfer pattern to a substrate is disclosed, the transfer mask made by forming an aperture pattern in a thin film portion supported by a supporting frame portion. When the transfer pattern includes a shielding pattern in which one part is connected to at least the periphery of the transfer mask, a shielding pattern portion, where the ratio of the surface area of the pattern surface portion on the transfer mask to a sectional area of a supporting portion is larger than 5000, is divided and developed.
